In automotive vehicle engine controls stepper motors responsive to microprocessor signals are often used to effect mechanical adjustments for engine operation. For example, EGR valves and idle air control valves are positioned by stepper motors by an engine control computer. Generally, such a computer is most effectively programmed to execute its program at a fixed rate, such as 160 Hz, and to issue a motor control pulse in each program loop when any motor operation is desired to yield a 160 Hz stepping rate. Such a fixed motor rate is accompanied by a fixed torque. At times it is advantageous to change either the speed of operation or the torque. This can be accomplished by changing the computer software but this is a major undertaking which may not be justified for the particular advantages to be gained.